Optimization of laser textured profiles for the thermal efficiency of heat exchangers produced in MAX phase

• Autor(a) principal: Reis, Rafaela Maia Sá
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/33713
• topic: MAX Phase; Cr2AlC; Plate heat exchanger; Micro-channel; Laser texturing; Concentrated solar power; Thermal analysis; Heat flux

The work developed in this Master thesis followed a multidisciplinary approach inside mechanical engineering, starting with materials science, machining technology and numerical simulation. First, the Cr2AlC MAX phase material was characterised, assessing its thermomechanical properties. Second, laser surface texturing (LST) was performed on Cr2AlC MAX phase material, and mixed texture combining corrugated surface and spaced channels were obtained by using a window of laser parameters previously studied. Last, a parametric study performing numerical simulations to obtain the maximum heat transfer, identifying the optimised geometry channels for a plate heat exchanger on concentrated solar power. Solidworks 2020 simulation software was used to analyse a molten salt’s temperature and heat flux over the Cr2AlC MAX phase and compare it with reference materials in this application, such as stainless steel 316L and alumina. Also, a parametric study was performed to determine the optimal width and depth configuration for the channels. Accordingly, with the results obtained in this work, it was possible to determine the thermomechanical properties of Cr2AlC. Mixed surface textures were obtained using the laser surface texturing (LST) technique, combining a corrugated surface and spaced V-shape channels with more than 350 µm of depth. Moreover, numerical simulations showed that ceramics materials have better heat transfer conditions than 316L stainless steel, where the Cr2AlC distance from alumina is 1.9% of heat flow. Also, corrugated surface increased heat transfer by 9.8%, and the optimal channels were found for LST conditions of 25 W in air and 20 s, with approximately 145 µm width and 340 µm depth. At last, a nondimensional tool was developed that can be used independently of the type of material.